Controlled stroke cylinder



A 1949- w. T. STEPHENS CONTROLLED STROKE CYLINDER Filed June 1, 1946 2 Sheets-Sheet l INVENTOR. WILL/AM 7- $TPHN5 ATTQE VEY mwn 145:! 1 lllll I 1 Patented Aug. 9, 1949 UNI OFFICE...

CONTROLLEDSTROKE CYLINDER I William T. Stephens, *Painesv-ille, 0hi0- Application J one 1, 1946,tSerialfNo. 673,805"

4 Claims. 3 z

My invention relates to hydraulic operating syste'msand concerns particularly systems" employing double acting cylinde'rsin which a piston is adapted to be moved" in either direction according'to the directionofapplication of fluid pressure,'or in which fluid-flow may be produced in one direction or another-according to direction of movement 1 of a piston in a double-acting cylinder.

It is an object of my invention to provide adjustment of lengthof stroke 'ofthepiston in hydraulic systems;

A further object. of the invention'is to provide means for .causing adjustment-of:stroke" to' be effected "byimeans ofthe same fluidpressure employed for operating the piston:

Still anotherobjectrof:theinvention is 'to. divert oil-:flow for the purpose of causing stroke length to be adjusted in one direction'or the other according to the direction oftoil-flow; produced by means: normally employed for producing motion in one direction or the other. of-the operator piston.

Other and further objects; .features and vadvantages of the invention will become apparent as the description proceeds.

In carrying out the inventionin; accordance with a preferred form thereof, I employ a doubleacting cylinder closed at the ends with fluid ports at either endand means forproducing flo'w of oil in or out at one end of the piston according to the direction which itiis desired to move the piston. In addition I provide means .for adjustingthe length of the stroke of a piston." Preferably this takes the form of a plunger mounted within the cylindenbtween .the piston and .the fluid port atoneend of the cylinder. The plunger is provided with a shank or rod protruding from the end ofthe'cylinder and packed inthe'manner of a piston rod. The plunger and the shank or rod thereof havea hollow bore'with'a connection external to the cylinderby means of which -the space within-the cylinder between the confrontingfaces ofthe piston and theplungermay com"- municate "with an external-conduit.

A source of fluid under pressure, 'such' as-an oil reservoir and gear pump, are provided" and a reversing valve-is provided to enable-either-the de' livery or the return-flow:- conduit of-*the'fiuid source to be connected-to'respective'ends of the cylinder. I Means are provided I for lockihg-- the stroke-control plunger-in a predetermined-position by closing'the fluid'port at-the' corresponding end of the cylinder:-and connecting'the bore'of reversing valve-so that the plunger face in effect serves as a --cylinder' "end-. For changing I the length-of stroke means are provided for clo'sine the-connection to the bore of'the plunger instead of to the corresponding end of the cylinder and connecting that end of the-cylinder to the fluid supply sothat when pressure is applied from the fiuid source the stroke controlle'dplunger is movedin one I direction orthe other *With' the piston-.-

A better understanding ofthe invention will be aiTorded by the following detailed description considered in conjunction with theaccompanyi-n'g drawin'g,-in which a v Fig. 1 is a schematic diagram of an embodiment of the invention showing the parts largely 101i gitudinal section with-the-fiow-reversirig-valv in neutral 'position Figi-2 is a fragmentary view 'in'lo'ngitud-inal section ofthe reversingvalve in the position-for causingthe-flow of fluid in suchdireetionas to move the piston to the right'as seen in Fig'a'h and Fig. -3 "is a 'schematicdiagram of the=system illustrating the fluid} flow-reversing valve 'inthe opposite position -'=fo-rproducing pisto'rrand plunger motion to the-left instead of -to the right and showing-the floW d-iVertingvalve in such 'a position as to clo'se th'e bore of the'strok-adj ust mg plunger so that the plungertravels conjointly with the piston:

Like reference characters are utilized throughout thedrawing to designate'like parts.

The embodiment of the invention illustrated in th-drawin'gs',-comprises a double acting'cylin 7 'der-l l a source of suitable fluid such as an oil reservoir l2, means for producing flow of the fluid in a driven direction'ywhich may take the form-of a gear pump =13, for example, aflowreversing valve 14, having a neutral position,'-'a flow-diverting valve l5 ','-and suitable inter-connectingpipes'orconduits". Although my invention maybe carriedout in connection with single"- acting cylinders and I may provide lengthof stroke-adjustment -in' single-acting cylinders; for thesake of illustrationpthe invention isshown and describedi'n' connection with a double-acting systerna Ac'cordin'gly; the cylinder H, as shown, is a double acting'cylinder having closed ends except'fo'r fluid ports ['6 and not the ends of the cylinder; A conventional piston 18 is-provided which is adapted to slide in th'e cylinder-"ll and hasa piston rod: l9 connected-thereto or integral therewith-for mechanical connection with apparatus to-be operated'by -the pisto'n l8 or'for-operating the piston--l8-jasthe -case-maybe-.

3 piston rod I9 extends through the left-hand end 2| of the cylinder I I and suitable packing is provided to prevent leakage.

In addition to the operator piston I8, there is a stroke-control plunger 22 adapted to slide Within the cylinder II. The plunger 22 likewise has a rod or shank 23 connected to or integral with the plunger 22 and extending through the opposite end 24 of the cylinder II. The shank 23 is likewise provided with suitable packing to prevent leakage through the opening in the cylinder end 24. However, the plunger 22 and its shank 23 are hollow or provided with a central bore 25 ex tending to a point 26 which remains outside the cylinder I I at the innermost position of the plunger 22. The outer end 26 of the bore 25 has a conduit 21 connected thereto, thus forming a connection exterior to the cylinder II from the space 28 in the interior thereof between the confronting faces 29 and 30 of the piston I6 and the stroke-controlled plunger 22 respectively. Preferably the conduit 21 consists of flexible tubing or a length of flexible tubing is joined thereto in order to permit free movement of the plunger shank 23.

The flow-reversing valve I4 is shown as being of the sliding-plunger type having a body 32 with a central bore 33 in which a plunger 34 i moved under control of an operating lever 35. The body 32 is provided with an inlet chamber 36 and an outlet chamber 31 separated by a folded wall 38 intersected in two ports 39 by the bore 33. The chamber 36 has an inlet opening or port 4| and the chamber 31 has an outlet openin or port 42. There is also a chamber 43 connected by a passageway to a first controlled port 44 and there is a second chamber 45 connected by a passageway to a second controlled port 46. The piston 34 is providedwith neck portions or reduced diameter portions 41, 48, 49 and 50, so positioned in relation to chambers 43 and 45 and the partition wall or diaphragm 38 as to leave the ports 39 open when the piston 34 is in a neutral position as illustrated in Fig. 1, and to close communication from the chambers 43 and 45 to either 1 the inlet chamber 36 or the outlet chamber 31. As will be described more in detail in connection with Figs. 2 and 3, the reduced diameter portions are so positioned as to open passageways from the chambers 43 and 45, in one direction or the other, to the inlet and outlet chambers when the piston 34 is moved in one direction or the other.

The flow-diverting valve I is also shown as being of the plunger type although the invention is not limited thereto. In the form illustrated, the flow-diverting valve I5 comprises a body 52 having a bore 53 in which a plunger 5| is adapted to slide. The bore 53 is provided with enlargements 54, 55 and 56 and the plunger 5| has a central reduced diameter or neck portion 51. The central chamber 55 has an external opening which may be referred to as a common port 58. The bore enlargements or chambers 54 and 56 have openings 59 and 6|! which may be referred to as first and second alternative ports respectively. The length of the plunger neck 51 is such that by moving the plunger 5| in one direction or the other the common port 58 may be connected to one or the other of the alternative ports 59 or 66. Preferably suitable means such as a spring 62 is provided for biasing the plunger 5| of the flowdiverting valve I5 to one of its two alternative positions. As will be explained hereinafter, the normal position is the position for which the cylinder end fluid port I1 is closed and the strokeadjusting or stroke-controlled plunger conduit 21 is open.

A conduit 63 is provided for supplying the pressure producing pump I3 with oil from the reservoir I2. A delivery conduit 64 is connected between the pump I3 and the inlet port 4| of the fluid-flow reversing valve I4, and a return conduit 65 is provided between the output port 42 of the reversing valve I4 and the reservoir I2. One of the controlled ports of the reversing valve I4, for example, the controlled port 44 is connected to the cylinder end fluid port I6 by means of a conduit 66 and the other controlled port 46 of the reversing valve I4 is connected to the common port 58 of the flow-diverting valve I5 by means of a conduit 61. The first alternative port 59 of the flow-divertin valve I5 is connected to the cylinder end fluid port I1 directly or by means of a length of conduit 68 and the flexible tubing or conduit 2'! serves for joining the bore 25 of the stroke-controlled plunger 22 with the second alternative port 66 of the flow-diverting valve I5.

Suitable means such as an operating lever or handle 69, for example, may be provided for shifting the plunger 5| of the flow-diverting valve I5 to the left-hand position, illustrated in Fig. 3, against the force of the biasing spring 62 when it is desired to change the stroke length of the piston I8.

When the plunger 5| of the flow-diverting valve I5 is in its normal or biased position and when the reversing valve I4 has its plunger 34 in its neutral position, illustrated in Fig. 1, both the piston I8 and the plunger 22 are locked in position in the cylinder II and the oil-flow produced by the pump I3 is returned directly to the reservoir I2. Owing to the fact that the portions of the bore 33 of the valve I4 are filled on either side of the chamber 43 by the full diameter portions of the plunger 34, no fluid flows into or out of the conduit 66 so that passage of fluid through the port I6 is closed and the piston I8 cannot move toward the left. Similarly the chamber 45 is closed closing the conduit 61, and the chamber 54 of the flow-diverting valve I5 is closed closing the conduit 68. The conduit 21 remains open to the conduit 61, but, since the conduit 61 is closed at the chamber 45 no flow of oil can take place from the right-hand end of the piston I8 or from the space II between the cylinder end 24 and the plunger 22. Consequently, the plunger 22 is locked in position and the piston I8 cannot move to the right. Oil cannot escape from the space 28 through the bore 25 nor can the oil be displaced by motion of the plunger 22.

Assuming that the flow-diverting valve I5 remains in the position illustrated in Fig. l, but, the reversing valve I4 is shifted to the right or to the left, oil flow through the conduits 66 and 61 takes place, causing the piston I8 to move in one direction or the other. For example, if the reversing-valve plunger 34 is moved to the right, to the position shown in Fig. 2, fluid enters through the conduit 64 into the inlet chamber 36 passage through the portion I2 of the valve bore around the reduced diameter portion 47 of the plunger 34 into the chamber 43 out through the conduit 66 into the fluid port I6 of the cylinder II, applying pressure to the left-hand face I3 of the piston I8, causing it to move to the right. Fluid from the space 28 is permitted to be displaced by the flow of fluid through the plunger bore 25, the conduit 21 into the chamber 56 of the flow-diverting valve I5, through the aawspeo agnrtion a! Irrotathe'walvexboreiamoundithe reduced 2111232181781 :portiomoniplungennecltdilgithronghsthe eicowrdnifzlt'lnntorthezdiamberiflknot thereversing EiWh/e :l 4;rthmuglr. a portionzi 5 miithenhoreiifi 330f ai'thezreversinggval-ve -21 remand .theaeduaedadiame- .t 5

awaken it isitdesiredstorichange :ithe; lengtlmof '30 'rthegpistomelii thisrisnaccomplislredrmy {mail insulin: phm'gerait tonbe movedaimronexidirsmctiomorzthezothet byzthemressurezofrtheisame epositionzithes pistons; I 8-:and-ithe plungeiii2r would 'iahavesbeen moved td the right instead bf tdithe left, the direction bf oil flow through theicondnit 1 ancESBmrerely Qhavingebeen revers'ed.

hile ihhaveirdescribed my inventiom-as ems ecie in concifete form and as operating-sin a :s'specificsmannen imeaccordancev witl'r' the provh ":r sions 'btith fitentlstatutesi it -should bwunderidstood that Ii doenotidimitany:inventiori therieto, mcvedsleftwarchtdttheiposi-? r1iy fisince: variousimodifications thereotrwill usuggest 'themselves-ite th'asesskilled in' theiart without deapartingrfromitheispirit-ofmyfinventionythe scope eiof which:.aisiseti'toithrin the annexedf'claims.

What-Iolaimtis:

i 2 hydrauiim operatingvsystemi :comprising ein zcofnbiniatiorr arsource of fluid un-der pressure -i'withi.deiiver w andrrieturn conduitss a -double 'aictcylinder havingi first zand second =fluid -ports-*'at a eitherxendr an operator piston siida'ble'in said cylfluid employed for moving the piston I8 and in iinder-aaiistroke controlt plunger in said py nder restzcnisexteahezsameisetting of the flow-reversing valve M. For example, if it is desired to shorten the length ofistroke;the reversing valve is moved ,to ,the ,leftrhand, position, -,i11u strat,ed in,.Ei g. 3,

and the plunger 5| of the.flowediuenting yalve;= J

H: is also moved to the left-hand position as illustrated in -l' igz 3. '-=In -this case oil delivered undempressure by the unp l3 enters through arti'ie :conduit 64, the inlet porter intosiihe inlet chamber 36 of the valve l4, passing through a portion 16 of the valve bore around the reduced diameter portion 50 of the plunger 34 into the chamber 45 and through the conduit 61. In this case, however, the portion 14 of the bore of the diverting valve 15 is closed and the fluid passes instead around the plunger neck 51 through the portion 11 of the valve bore into the chamber 54 out through the first alternative port 59 through the conduit 68 and into the space H in the cylinder II. This action exerts pressure on the back face 18 of the plunger 22 forcing it to the left.

Since the portion 14 of the bore of the diverting valve 15 is closed no fluid can escape through the bore 25 or the outlet conduit 21 of the strokecontrolled plunger 22 and accordingly the lefthand motion of the plunger 22 exerts pressure upon the fluid within the space 28, which can be relieved only by movement of the piston l8 which accordingly moves to the left in response to the pressure acting upon its face 29. The fluid to the left of the face 13 of the piston I8 is permitted to escape through the port It, the conduit 56 back to the reservoir l2 through the chamber 43 of the reversing valve l 4 around the plunger neck 41, through the port 19, to the outlet chamber 31 and through the return conduit 65.

Thus, the plunger 22 and the piston l8 are caused to move conjointly. They move exactly in unison except for any lost motion which may be produced by presence of compressible fluid or air in the system or any leakage which may take place. Any such lost motion or leakage, however, does not interfere with the function of the apparatus in adjusting the stroke since the flow-diverting valve It will be left in its stroke-adjusting position until the desired adjustment has been eifected, whereupon it will be allowed to resume its normal position under the force of the spring 62 and any correction in movement of the piston I8 is effected by appropriate manipulation of the reversing valve I4. It is manifest that if the reversing valve l4 had been in the right-hand position instead of the left-hand position when the diverting valve l5 was shifted to the control abetween said ipistom and the second-cylinder -fl uid ortszsa id iplunger having a bore- 'w ith a eonnecomtoa conduit' external to the cylindeia a flowiuertingkvalve; and a" flow-'reversing valve said a .flow-divertingrvalv whaving first and second e alterifa'tive portsand a common port 'vvith-means ator connecting ithe com-mon port 1302 one or lthe her- -foii thee.'aiternative ports and' bloclrin 'the iconn'e ttioniofithe-common port to the other" alterzrative porta af fluid conne'ction between the-second cylinder port and'ithei first divei'ting valve port, said plunger conduit being connected to the second diverting valve port, said reversing valve having input and output ports joined to the de- 5 livery and return conduits respectively of the fluid source, first and second controlled ports and means for alternatively connecting the first controlled port to the input and the second controlled port to the output port or vice-versa, a A connection between the first cylinder port and the first reversing valve control port, and a connection between the second reversing valve control port and the diverting valve common port; whereby the reversing valve normally controls direction of movement of said operator piston in response to pressure of said fluid, and the strokecontrol plunger remains stationary, but, shifting of the diverting valve to its first port connection causes the reversing valve to control direction of movement of the stroke-control plunger together with said piston.

2. An hydraulic operating system comprising in combination a source of fluid under pressure with delivery and return conduits, a double-acting cylinder having first and second fluid ports at either end, an operator piston slidable' in said cylinder, a stroke-control plunger in said cylinder between said piston and the second fluid cylinder port, said plunger having a bore with a connection to a conduit external to the cylinder, a flowdiverting valve and a flow-reversing valve, said flow-diverting valve having first and second alternative ports and a common port with means for connecting the common port to one or the other of the alternative ports, a fluid connection between the second cylinder port and the first diverting valve port, said plunger conduit being connected to the second diverting valve port, said reversing valve having input and output ports each joined to one of the fluid source conduits, first and second controlled ports, and means for alternatively connecting the first controlled port to the input port and the second controlled port to the output port or vice-versa, a connection between the first cylinder port and the first reversing valve controlled port and a connection between the second reversing valve controlled port and the diverting valve common port.

3. An hydraulic operating system comprising in combination a source of fluid under pressure with delivery and return conduits, a double-acting cylinder having first and second fluid ports at either end, an operator piston slidable in said cylinder, a stroke-control plunger in said cylinder between said piston and the second fluid cylinder port, said plunger having a bore with a connection to a conduit external to the cylinder, a flowdiverting valve having first and second altemative ports and a common port with means for connecting the common port to one or the other of the alternative ports, a fluid connection between the second cylinder port and the first diverting valve port, said plunger conduit being connected to the second diverting valve port, a connection between one of the fluid source conduits and the first cylinder port and a connection between the other fluid source conduit and the diverting valve common port whereby the setting of said flow-diverting valve to the second alternative port connection results in locking of the stroke-controlled plunger and movement of the operator piston according to direction of fluid control or vice versa, and a setting of the diverting valve to the first alternative port connection the stroke-control plunger.

4. Variable stroke hydraulic apparatus comprising a double-acting cylinder, an operator piston in said cylinder, a stroke control plunger in said cylinder, a flrst fluid port in said cylinder disposed between said operator piston and one end of the cylinder, a second fluid port in the cylinder disposed between said stroke control plunger and the other end of the cylinder, a third fluid port leading to the space between said operator piston and plunger, valve mechanism connected with said second and third ports and having port means for connection with a fluid circulating system, said valve means being arranged so that with the valve means in one position it connects said valve port means to said second cylinder port and blocks the third cylinder port whereas with the valve means in another position it connects said valve port means to said third cylinder port and blocks said second cylinder port.

WILLIAM T. STEPHENS.

REFERENCES CITED UNITED STATES PATENTS Name Date Pelton June 18, 1935 Number 

